EFFECT OF THERMAL AND SOLIDIFICATION BEHAVIOUR ON CHARACTERISTICS OF PULSED CURRENT GMA WELD

Abstract

The difficulties in simulation of GMAW process with respect to its thermal behaviour and weld geometry of weld pool are primarily caused by various metal transfer mechanisms occurring at different welding parameters, dictating the heat of the arc imposed on the surface and the transfer of heat by penetrating droplets inside the weld pool. However, in P-GMAW process the spray mode of metal transfer always takes place at high peak current but, in case of any metal transfer at the base current it usually follows a globular free flight transfers. Therefore it is realised that in this process the heat transfer to weld pool is composed of the arc heat and sequentially deposited molten metal droplets superheated up to different extent depending upon pulse parameters. The analytical studies on the heat transfer by transferring droplets inside. the weld pool of GMAW process are found close to the experimental observation but, in spite of several efforts, hardly any convincing work has been reported so far for estimating the final thermal behaviour of P-GMA weld pool. In some earlier works on general arc welding the use of a concept of double ellipsoidal power density moving heat source to find an appropriate solution for estimation of temperature distribution in weld has been found effective to match the experimental observations. But, satisfactory analytical solution for the temperature distribution and peak temperature of the weld pool in P-GMAW process is not also well known.